Photoflash lamp

ABSTRACT

A photoflash lamp employing ignition by means of electrical breakdown in which the ignition mass is provided on an electrically insulating body which is covered by two thin layers of metal serving as electrodes and being connected to the current conductors. The electrically insulating body including the ignition mass is provided within the envelope which furthermore contains a metal wire filling and an oxidizing gas.

United States Patent Meulemans et al. [451 Aug. 22, 1972 [s41 PHOTOFLASH LAMP 3,224,236 12/1965 DeMent ..43l/95 x [72] Inventors: Charles Camus Eduard Mew 3,501,254 3/1970 Ni land ..43l/95 lemans; Johannes Cornelis Van Der Tas, both of Temeuzen, Netherlands Primary Examiner-Edward J. Michael [73] Assignee: U.S. Philips Corporation, New 7 Attorney-Frank Tnfan York, N.Y.

[22] Filed: Oct. 5, 1970 [57] ABSTRACT [21] Appl' 77301 5 A photoflash lamp employing ignition by means of electrical breakdown in which the ignition mass is pro [30] Foreign A li ti P i i Data vided on an electrically insulating body which is covered by two thin layers of metal serving as elec- Y The electrically insulating body including the ignition mass i within the envelope 58 Field of seareh...................1...I:.1:I i i)93, 94, 95 g? a metal We finmg and [56] References Cited 2 Clains, 7 Drawing Figures UNITED STATES PATENTS 2,771,765 1 1/1956 Arnott et al. ..431/95 x PATENTEDwczz mzz PHOTOFLASH LAMP X The invention relates to a photoflash lamp including an envelope of light-transmitting material and two current conductors protruding from the lamp, a combustible material, and oxidizing gas and an ignition mass being present within the envelope and the end facesof the current conductors within the envelope being in contact with the ignition mass which is provided on a body of electrically insulating material encompassing at least part of the two current conductors within the envelope.

In such a photoflash lamp the envelope consists of, for example, glass and is provided with one or more optionally blue-colored lacquer layers. Furthermore the lamp has at least one pinch through which the current conductors are passed.

The envelope contains a combustible material such as a wire filling of zirconium, and oxygen is generally used as an oxidizing gas. The current conductors within the envelope are usually fixed relative to each other by means of a body of electrically insulating material, for example, of glass or a ceramic material which encompasses at least part of the conductors located within the envelope. An ignition mass which explosively burns upon ignition is present on the body of electrically insulating material. During this combustion incandescent particles within the envelope are hurled away and initiate the actinical light-producing reaction between the combustible material and the oxidizing gas.

The ignition mass generally consists of a mixture of an oxidant such as potassium perchlorate, a metal powder, for example, zirconium and a binder such as nitrocellulose. This mass is ignited by connecting the current conductors to a suitable voltage source. An electric breakdown in the mass is then effected which evolves heat and brings the mass locally at the ignition temperature.

In such a lamp it is desirable that:

a. the distance between the end faces of the current conductors which are in contact with the ignition mass is small and is maintained constant as much as possible within certain limits for each lamp during manufacture;

the dimensions of the part of the current conductors which is in contact with the ignition mass is as large as possible but is maintained constant as much as possible for each lamp during manufacture;

. the distance between the end faces of the current conductors being in contact with the ignition mass is smaller than the distance between an arbitrary point of such an end face and a part of the surface of the ignition mass accessible to the combustible material.

Only if the lamp satisfies these requirements is it ensured that the ignition of the actinical reaction proceeds faultlessly and that the lamps be used in a parallel arrangement in which the lamp to be ignited is selected by means of the ignition voltages of the parallel arranged lamps. If, for example, requirement is not satisfied by all lamps, there is the risk that the applied voltage in a lamp leaks away to the combustible material without reaching the ignition voltage of any lamp in the circuit.

It is an object of the present invention to provide a construction in which the previously mentioned requirements are satisfied.

To this end a photoflash lamp according to the invention is characterized in that the end faces of the current conductors substantially coincide with the surface of the body of electrically insulating material and are each in electrical contact with their own electrically conducting layer provided on the surface of the body, and that the ignition mass is provided on the conducting layers which do not establish mutual electrical contact, the ignition mass shunting the non-conducting part of the surface of the body between these electrically conducting layers. The substantial coincidence of the end faces of the current conductors with the surface of the body of electrically insulating material is understood to mean that the end faces of the current conductors do not essentially extend more above the surface of the body than the thickness of the electrically conducting layers on this surface. The thickness of the electrically conducting layers may be, for example, between I and um.

According to an advantageous embodiment of a photoflash lamp the electrically insulating body is provided with a groove located centrally between those points of the surface of the body where the surface is penetrated by the current conductors and is directed at right angles to the line of connection between these points. The raised edges of the groove are then coated with electrically conducting layers which are in contact with the end face s of the current conductors. The bottom of the groove is not coated with an electrically conducting layer. This embodiment has the advantage of increasing the number of possibilities of ignition mass breakdown.

The electrically conducting layers may be provided by a number of different methods. Some of these methods will be briefly described hereinafter, because these methods as such are considered to be sufficiently known to those skilled in the art. The surface of the body of electrically insulating material intended for this purpose is provided with an electrically conducting layer of metal or a conducting compound such as SnO In O for example, by means of vapor deposition, sputtering, by an electroless method, electrolysis or, for example, with the aid of a metal lacquer. In this case it is possible to coat the surface directly with two layers which do not establish mutual electrical contact, for example, by using a mask. Alternatively, after an electrically conducting layer is provided on the entire surface, it is possible to remove part thereof, for example, by means of an etching method while covering part of the layer with an etching resist or by mechanical removal of the metal layer.

In order that the invention may be readily carried into efiect, several embodiments thereof will now be described in detail, by way of example with reference to the accompanying diagrammatic drawing, in which FIG. 1 is a perspective elevational view of a body of insulating material without an ignition mass,

FIG. 2 is a cross-sectional view of the body of FIG. 1, taken on the line II-II including an ignition mass,

FIG. 3 and FIG. 4 are plane view of bodies of insulating material on which conducting layers have been provided in accordance with difierence patterns,

FIG. 5 is a perspective elevational view of a preferred embodiment of a body of insulating material,

FIG. 6 is a cross-sectional view taken on the line VIVI of the body of FIG. 6 including an ignition mass,

FIG. 7 is a cross-sectional view of a photoflash lamp including a body according to FIG. 6.

In FIG. 1 the reference numeral 1 denotes a discshaped body of electrically insulating material. Such a body may consist of, for example, glass. Two current conductors 2 and 3 are secured in the body 1 by means of sealing in or in a different manner suitable for this purpose. Each current conductor is in electrical contact with its own electrically conducting layers 4 and 5, respectively.

For the sake of clarification FIG. 2 illustrates a crosssectional view of the body 1 etc. taken on the line II)I of FIG. 1. However, this Figure also shows the ignition mass 6.

FIGS. 3 and 4 show a few configurations of electrically conducting layers. The metal layers 4 and 5 may be obtained in accordance with the shapes shown, for example, by first providing a metal layer at a thickness of approximately 25 pm, for example, by means of vapor deposition in vacuo on the surface of the body I intended for this purpose. Subsequently a photoresist is provided on the metal layer. The photoresist is exposed in accordance with the desired pattern and is subsequently developed. The parts of the metal layer bared during development are subsequently etched away. The part of the resist layer left during development is the removed and the ignition mass 6 is provided.

FIG. 5 illustrates a perspective elevational view of a preferred embodiment of a body 1. This body 1 is provided with a groove 7 whose raised edges are coated with electrically conducting layers which form part of the conducting layers 4 and 5.

FIG. 6 also illustrates a cross-sectional view taken on the line V-V of FIG. 5, and this Figure also shows the ignition mass 6.

FIG. 7 illustrates a cross-sectional view of a preferred embodiment of a photoflash lamp according to the invention, in which parts of the current conductors 2 ad 3 are sealed in in the pinch 10. A (zirconium) metal wire filling 9 is present within the envelope 8.

What is claimed is:

l. A photoflash lamp of the type having an envelope of light transmitting material, two current conductors protruding from the lamp, a combustible material, an oxidizing gas, and an ignition mass, wherein the improvement comprises:

a body of electrically insulating material;

two independent electrically conducting layers disposed on the top surface of the body, each of the current conductors being brought through the body to respective layers and forming electrical contact with said layers, electrical contact being avoided between said layers allowing surface exposure of a non-conducting portion of said body, the end faces of the conductors substantially coinciding with the top surface of the body, said ignition mass being disposed on the conducting layers and shunting the non-conducting portion of said body between said layers.

2. A photoflash lamp as claimed in claim 1 wherein the surface of the body of electrically insulated material is provided with a groove located centrally between those points of the surface of the body where said surface is penetrated by the current conductors and is directed at right angles to the line of connection between said points, the independent conducting layers extending to the vert ical edges pf said grooves. 

2. A photoflash lamp as claimed in claim 1 wherein the surface of the body of electrically insulated material is provided with a groove located centrally between those points of the surface of the body where said surface is penetrated by the current conductors and is directed at right angles to the line of connection between said points, the independent conducting layers extending to the vertical edges of said grooves. 